The knowledge of the cnc tube bending machine—Try to avoid bending wrinkles
When the cnc mandrel tube bending machine is running, the material inside the centerline is compressed. When bending to a certain angle, the material will be pushed back and beyond the tangent point due to the large compression force. If the pipe wall in this area is not supported by the bending die, the wrinkles will be formed. Even if this area is flattened by mandrel and bending die, the wrinkles cannot be eliminated. And it will form a large wrinkle when bending completed.
The use of anti-wrinkle die can increase support in this area. This can uniformly thicken the pipe wall after compression without any wrinkles.
The shape of the anti-wrinkle die is very important. The groove size of pipe sliding should be slightly larger than the outer diameter of the pipe; it can be 10% of the wall thickness. The groove also needs to be polished carefully to prevent pipe scratches.
The front section of anti-wrinkle die should be made very thin so that can extend to the tangent point of the bending die. It is supported by the bending mold and fixed to form a closed cavity. To reduce the resistance during bending, the anti-wrinkle die should have a small taper during installation. The pressure of the die should also be adjusted properly. It is better to install and adjust the anti-wrinkle die when the clamping die is tightened, and use the function of “adjust mandrel”.
When cnc tube bending machines is running, the anti-wrinkle die should be coated with an appropriate amount of oil. Too much or too thick oil will also cause wrinkles in this area.
The machine is also equipped with ball mandrel while using anti-wrinkle die. The function of the anti-wrinkle die is to prevent wrinkles; and the ball mandrel can keep the tube from collapsing after leaving the mandrel support point.
When bending pipes with thin wall, large diameter and small bending radius, the following points should be noted in order to avoid wrinkles:
① Reduce the resistance between mandrel and the inner wall of the pipe during bending. The inner chamber of the pipe needs to be blown by wet sand before bending.
②The machine tool and spindle should rigid enough.
③The mandrel should rigid enough to eliminate the shaking and stretching caused by the rod.
④The radial clearance between mandrel and the inner diameter of pipe shouldn’t be greater than 10% of the wall thickness.
⑤The clamping die, pressing die, mandrel, and anti-wrinkle die should be adjusted properly. In particular, the pressure of clamping die should be carefully selected and adjusted.
When bending pipes with large diameter, the clamping of clamping die is also a prominent problem. In this case, the straight line between the two bends of the pipe needs to be longer and the clamping die needs to be wider. This can increase the clamping force and ensure the bending process. If the clamping die is too narrow, there is not enough clamping force. The pipe will slip and the bending process will stop immediately.
⑥ Select an appropriate amount of lubricating oil.
⑦The supply status of materials is also very important. For example, the stainless steel pipes, the hardness is HB=180～220, and the HB=180 is the most suitable hardness.
As one of the most reliable cnc tube bending machine manufacturers in china, we not only provide high-quality hydraulic pipe bender and CNC pipe benders for customers all over the word, but also welcome customers to discuss the technology of pipe bender with us. We can improve the performance of pipe bender in practice to make our machines are more in line with customer needs.